Data storage devices using various kinds of media such as an optical disk and a magnetic tape have been known in the art. In particular, a hard disk drive (HDD) has been widely used as a storage device of a computer and has been one of indispensable storage devices for current computer systems. Moreover, the HDD has found widespread applications such as a removable memory used in a moving image recording/reproducing apparatus, a car navigation system, a cellular phone, and a digital camera, as well as the computer, due to its outstanding characteristics.
A magnetic disk used in the HDD has a plurality of data tracks concentrically formed, and respective data tracks are divided into a plurality of sectors. On the recording surface of the magnetic disk servo data are recorded discretely in the circumferential direction. A spindle motor rotates the magnetic disk and a head element portion of a thin film element accesses a desired address position in accordance with the servo data to write/read data to/from the magnetic disk.
The head element portion is fixed to a head slider and these constitute a head. The head is attached to a suspension. The head slider flies over the rotating magnetic disk to position the head or the head element portion to a desired position above the magnetic disk. In a data reading process, a signal processing circuit performs predetermined signal processes such as waveform shaping and decoding on signals read out by the head from the magnetic disk and sends them to a host. The signal processing circuit also performs predetermined signal processes on transferred data from the host and writes them onto the magnetic disk.
A HDD, in particular a HDD used for such as a notebook, a car navigation system, or a mobile purpose, sometimes receives a strong external impact. If it receives a strong external impact, the head is lifted off from the magnetic disk by more than a prescribed fly-height to cause a data error that writing data and/or reading data cannot be performed, for example. Or, the head contacts the magnetic disk to scratch the magnetic disk or cause a head crash at worst. Accordingly, in the HDD used for a purpose in which a strong impact is likely to be applied, various measures against data error, a breakage of the magnetic disk, a head crash, and the like have been taken to attempt to improve impact resistance.
As one of the measures against an impact to the HDD, the loading/unloading scheme that retracts the head from above the magnetic disk in a non-operation time has been adopted. In the loading/unloading scheme, a ramp is used. The ramp has comb-like slits through which the magnetic disks pass and tab slides on which tabs of an actuator slide. This ramp is disposed at a side of the magnetic disks so that the slits overlap parts of the outer ends of the magnetic disks. The tabs on the tip end of the suspension ride on the tab slides so that the heads are retracted to the outside of the magnetic disks. Thereby, if any impact is applied during a non-operation time, a crash of the magnetic disk and the head is avoided.
In a HDD with the loading/unloading scheme, a data error occurrence problem has been observed even if such a strong impact as described above has not been applied. Oscillation of the rotating magnetic disk sometimes causes contact of the disk with the ramp in an operating HDD to scrape off the ramp. If the ramp is scraped off like this, dusts are generated within an enclosure of the HDD. The dust particles are spattered over the disk and if the head performs reading or writing operations in this state, the head rides on the dust particles so that an error may occur.
It has now been revealed that such contact of the magnetic disk and the ramp is raised by a smaller impact than the foregoing strong impact. Japanese Patent Publication No. 2001-101814 (“Patent Document 1”) discloses an example that a squeeze plate for eliminating oscillation in the rotational axis direction of the magnetic disk, is provided at the outer diameter side of the magnetic disk to eliminate oscillation of the magnetic disk and prevent the magnetic disk and the ramp from contacting each other.
If a squeeze plate can eliminate oscillation of the magnetic disk as described in the Patent Document 1, contact of the magnetic disk and the ramp can be prevented. Consequently, it is supposed to prevent that the rotating magnetic disk contacts the ramp to scrape it. However, providing a squeeze plate causes an increase of the number of components. Besides, in the HDD with a design that the squeeze plate is not used, contact between the magnetic disk and the ramp cannot be avoided. Although the squeeze plate eliminates the oscillation of the magnetic disk, if the magnetic disk and the ramp contact with each other, there still remains the problem that the ramp will be scraped off.
Therefore, it is desired to prevent occurrence of data error by decreasing generation of the dusts due to the contact of the magnetic disk and the ramp caused by a relatively small impact and thereby to improve impact resistance during operation of the HDD.